A standard diverter-type faucet assembly such as described in U.S. Pat. No. 3,056,418 of Adams has a diverter chamber provided with a diverter valve and connected on one side at a faucet outlet port with the faucet and on the other side via a diverter port to a hose leading to a secondary user, such as for instance a sprayer or a dishwasher. As is standard, when pressure in the hose connected to the diverter port is low when the sprayer or dishwasher valve is open, the diverter valve sends flow to the diverter port instead of to the faucet port.
This arrangement is also provided with an antisiphon or antibackflow vent that opens into the feed passage from which mixed water is fed to the diverter chamber. Thus if pressure in this feed passage drops below atmospheric pressure, the vent opens and the system will suck air rather than sucking water back out of the downstream lines.
Such an arrangement is not only fairly complex, but does not respond in all situations. Water can in fact get from the diverter hose back into the diverter chamber and, in the event of a serious underpressure in the feed passage, can be aspirated into the feed lines.